If the trigger mechanisms were properly maintained, they'd be viable, usable, and easily transported.

Quoting: DarthDickheadus:AmericanSith

The average person would not recognize a nuclear weapon. A lot of them don't look anything like bombs.

The best-case scenario for an actual first echelon strike, in a real nuclear war, would be about 1500 warheads detonating inside the US at about the same time. From the time they decide to launch to the time the fate is inevitable is about FOUR MINUTES.

If anyone intends to use a nuclear weapon, it will not be done to kill people but to get a nation to retaliate with full-scale nuclear assault. These dramatic attacks, like 911, are not done to accomplish anything except instigating a fight between larger powers with better weapons.